Valve



Aug. 19, 1952 B. w. 4MANTLE VALVE Filed July 8, 1946 INVEN TOR.

BWM L T N A, MM w. RM R U B ya B FIG.2

S Y E N R O T. T A

Patented Aug. 19, 1952 VALVE Burr W. Mantle, Pittsford, N. Y., assigner to American Brake Shoe Company, Wilmington,Y Del., a corporation of Delaware Application July 8, 1946, Serial No. L682,060

v 2 Claims.

' This invention pertains to a valve and particularly to Van unlo'ader valve of the type designed for use' with'fluid compressors and the'like.

In' order to prevent damage to electric motors of aV type commonly used for driving compressors, it is necessary to permit such motors to reach an operating speed where heavy currents of electricity, as are used for example in the starting windings, may be reduced or Where special windings may be thrown out of operation before sufficient time has elapsed for the windings tobecome loverheated Whileth-is applies particular# ly to motors of the alternating current repulsioninduction type, it applies also, although perhaps to a lesser extent,- to other electric motors. Most of ythe various electricfmotors in use are subject to overheating and damage ifA operated under heavy-load at'greatly reduced speeds forappreciable periods of time.

Hence for the purpose of taking ,the Vload ofi a compressorat timeswhen: heavy current is being drawn'v as, for example,y during starting, it is desirable to provide a. simple and veffective mechanism which will .be automatic in operation. Various mechanisms have been designed in the past for accomplishing this purpose but some of them `have been complex-and certainones have lack-ed reliability in operation. Compressors such asthose usedfor compressing air for various purposes, aniparticularly. compressors of small or medium sizes driven vby electric motors, require a means for relieving the pressure during starting operations. As pointed out above, most velectric motors will overheat at low speed andthis is particularly true vof those provided with auxiliary starting windings which are required to carry large currents of electricity for short periods, the starting torque vof the Vregular operating windings being inadequate.v Starting windings of this type are usually not designedfor `operation over extended periods of 'timejand in `fact are commonly subject to overheating and possible burning out if their use is long continued.

Accordingly, it is an object of my invention to unload a compressor'of the type mentioned above during'starting operations by mechanism which is responsive to the lspeed-at which the compressor is being driven and -to the Avolume of its output, such mechanism permitting compressed fluid to escape until `a desired minimum loperating speed has been attained. v i

A further object is to unload a compressor by automatic means during thestarting period and toautomatically and positively 'close suchunloader when a desired minimum operating speed hasbeenreached. iv

A still furtherobject is to automatically unload a compressor whenever it is operating below a predetermined minimum operating speed by releasing compressed fluid through means which are responsive to the rate of now of such fluid, such means being operable to stop such flow when the volume of Vfluid being compressed per unit of time reaches a predetermined level corresponding to said predetermined speed.

Another object is to unload afluid compressor or the like by releasing the fluidycompressed through Va restricted opening in anv unloader, which 4opening is so formed kas to become increasingly restricted, land thereby to accelerate a closing operation as the operating speed of the compressor reaches a desired minimum rate. Still another object is to prevent, by positively operating means, the release of fluid Athrough said unloader when the speed of the compressor or the volume of fluid being compressed per unit of time reach predetermined values.

Other and further objects of the present invention will be apparent from theV following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred embodiment thereofv and what I now consider vto be the best mode iny which I have contemplated applying these principles. Other embodiments of vthe invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing-from the present invention and the purview of the appended claims.

In the drawings :V

Fig. 1 is an elevationalview'ofl an embodiment of my invention consisting of a volume responsive unloader; and

Fig. 2 is a vertical sectional View on a somewhat larger scale of the mechanism shown in Fig. l, taken substantially along the line 2*-2, Fig. 1.

As shown in Fig. 1,'the volume unloader of my invention is indicated generally at ll and isv applied to a part, for example, the cylinder 'head l2, of a ud .compressor which maybe, for example, an air compressor, not shown. The unloader consists of a hollow base member orreceptacle 13 provided with a connecting shank portion I4 which containsa fluid. passage and is threaded into an appropriate opening in a cylinder head I2 or the like.

Above the basemember i3 kthe unloader inclndesa body portion 1.5 formed of suitable material such as metal, or the"4 like, and provided with a threaded opening I .6 .which'may receive a tube or pipe connection ll. If'the compressor is used for air, the pipe I1 may be omitted if desired or may lead merely to the atmosphere. If used for other materials where it is not desirable to discharge them to the atmosphere, the pipe or tube I1 may be used to return fluid released therethrough to the low or intake side of the compressor system in order to avoid loss of uid to the atmosphere. An example of the latter is an application of the unloader to the compressor of a mechanical refrigerator.

The body portion I is surmounted by a cap I8 which may be molded or drawn of suitable material, for example, plastic or sheet metal. This cap is designed to cover certain working parts, to be described hereinafter, and it may rest against a shoulder formed on the upper part of the body member I5 as indicated at I9. The cap I8 may be knurled as at 2 I, 22 and the body member may be knurled as at 23. The base member I3 may be knurled as at 24, 25, for 4holding manually when the various parts are assembled ordisassembled.

The internal construction of my improved unloading valve mechanism is clearly shown in section in Fig. 2. Below the cylinder head or the like, I2, a compressorpiston or equivalent element, not shown, may be operating, or a rotary type compressor unit maybe used, the operation of the unloader being suitable for either type.

The shank portion I4 of the base member I3 is provided with an internal passage 3| for uid which passage may be of a size adequate to permit flow of fluid without materialre'sistance up to the minimum operating speed of the compressor. At such speeds, where the compressor is driven by a repulsion-induction type motor, the counter-electromotive forces in the motor are such as to prevent the ilow of excessive current in the running windings, and the starting windings are normally thrown out of operation. In general, the same considerations apply to other types of electric motors so there is little danger of damage after an operating speed of '75 to 90 percent of full speed is reached.

The passage 3| leads to a pressure chamber 32,

` the lower part of which is formed within the enlarged upper portion of the base member I3. Above the shank I4 and within the pressure chamber 32, the opening 3| is partly closed by a disk element 33 which is provided with a. centra1 perforation 34. This disk 33 is normally held down against the bottom of the pressure chamber 32 and in position to partly close the port 3| by a coil spring 35, the upper end of which is held down by an inwardly projecting flange or ring member 36 suitably secured to the interior side walls of the base memberl3. The lowermost turn of the spring 35 surrounds an upwardly projecting flange 31 on the disk 33 and thus holds it in a position directly over the opening 3|. -The perforation or opening 34 in the disk 33 is of a size to permit a certain restricted ilow of uid, such as compressed air, for a purpose which will be described hereinbelow.

The body member I5 is threaded externally as at 4I to t within internal threads 42 of the base member I3. The lower annular wall portion of body member I5 is tapered, as indicated at 43, to form a converging chamber toward the top of recess or chamber 32. The space thus surrounded by the tapered wall portions 43 and by the upper part of the base member I3 comprises a pressure chamber which is designed to operate certain valve mechanism next to be described.

A floating valve member consists of a disk 5| positioned transversely within the pressure cham- 4 ber 32 and of such a diameter as to permit restricted flow of fluid about its edges and within the tapered walls 43.A The disk is secured to a cup shaped member 52 which is threaded internally to receive a threaded retainer 53 for the enlarged head 5 4 of a vertical rodA orsleeve 55. A resilient disk 56 is providedin the'bottom of cup 52 and this serves to support the head 54 of rod 55 when the threaded retainer 53 is tightened into the cup. By these means the disk 5|,

oup 52 and rod 55 are secured together, certain resilience between them being provided to prevent shock to operating parts as the valve is quickly closed oropened.

The valve rod or stem 55 consists of the lower portionto which the valve disk is attached and an upperportion 58 of somewhat smaller diameter than the lower part. At the shoulder 59 where these two parts join, a washer 60 is slidably mounted on the rod.' The upper end of the rod is threaded externallyV as indicated at 6| and a sleeve element 62, provided .with a ilanged base portion 63fat its lower end, is threaded internally at its upper end, as shown at 64, to receive the threaded portion 6| of the rod or stem 55. The upper end of the st em 55 is slotted or notched as indicated at 65 to receive a' screw driver or like tool for adjusting the stem longitudinally with respect to the sleeve element 62. A lock nut 66 is threaded on to the rod or stem 55 and serves to lock these parts in lany adjusted position. l

By the constructionA just v described, vertical movement of the disk 5 I Vis 4accomplished by similar movement ofjthe rod or stem 55, the washer 60 and the flanged sleeve 62, these parts allbeing secured together. Such movement is restricted by a light coil spring 68, the lower end of which rests on the ilange 63. The upper end Vof spring 68 is held down by the lower end of Va vertically adjustable sleeve or bushing member 1|. This member is provided externally withthreads 12A which t into internal. threads 13 of another sleeve or bushing member 14. Thev bushing member 14 likewise is externally threaded as shown at 15 to be screwed intointe'rnalv threads 16 formed'in an upper recess in the body member I5. A look nut 11 is provided tohold the sleeve 1I in adjusted relation with respect to the outer sleeve 14.y Likewise, a lock nut 18 Yisprovided'to hold the sleeve 14 in adjustment with respect to the body member I5. Y

The bushing orvsleevemember 1 4 has a downwardly projecting hollow shank portion 19 which surrounds the light coil spring 68 and is surrounded byanother and much'heavier coil spring 8|. The upper end of vthe coil'spring 8| abuts against a'shouldery 82 formed Von the bushing or sleeve member .14.. The lower end Vof this spring rests on a washer 83 which sets against a shoulder 84 formed in the bottom 4of a recess .85 in the upper part of the body member I5.

The parts just described'are so assembled that the rod or stem-55 and thelassociated parts, in` cluding the flow restricting valve disk-5|, tend to be held down by the light coil spring 68. Tension on this spring-is adjusted, asnnoted above, by adjustment of the sleeve' member'1lj Tension on the heavy spring 8| which holds down the disk or washer 83 'isadjusted by turning the bushing or sleeveV member 14" in. the threads formed inthebodymember I5. f J 1 In addition to the tapered wall portion 43 mentioned above, the recess in the lower end of the body -member |5 comprises a cylindrical portion 9| which is very .slightly larger in 4diameter than the valve disk 5.|`, and an 'internally threaded recess92 for a valve seat member 93. The valve seat member is providedv with a central aperture 94 which is largeenough to 'prov-ide a port for fiuid flow around Vthe stem 55, as will beV described hereinbelow. The valve disk 5| is adapted to seat against the Vseat 93 when in its fully raised position. In such position it prevents further now of uid, such as compressed air, through the unloader.

The cup member 52 at the lower end of the valve stem 55 is also positioned above the disk 33 a distance at least sufficient to permit the `free flow of fluid Afrom the compressor through the port 34 in disk 33. Flow of Viiuid, whenthe unloader is operating, is upwardly through the v.passage 3 through the port134yor under the disk 33 lif the latter is raised due to pressure in the com-Y pressor, thence upwardly through the pressure chamber 32 through the washer 36, around the outer edges of the disk 5|, through the aperture 94 surrounding the valve stem, and thence out through the opening I6 to the tube l|'| and to the atmosphere or to the low side of the compressor. 'Ihe opening 34 is smaller in effective cross section `than the aperture 94 and the aperture 94 is slightly larger than the outlet lport I6. The

opening 34 is `of such a size that iluid forced into the chamber 32 cannot -all flow back into the compressor during a single cycle thereof when the compressor is operating above starting speed. Fluid may be forced into the chamber 32 by the compressor more easily, however, because the disk 33 acts somewhat as a check valve, permitting a large inflow from below but restricting flow from above. The result is that at least some pressure is maintained within the chamber 32 under all operating conditions although when the compressor is being operated slowly this pressure maybe very small.

When the pressure in the-chamber 32 is very low, as it is when the compressor is just starting, fluid iiows gently around the edges of the valve disk 5| and out through the openings 94 and I6, very little load being imposed on the compressor. As the speed increases, the pressure in chamber 32 increases very gradually at rst, but when the velocity of flow past the disk 5| becomes suicient to start lifting this disk against the tension of the light spring 68, the valve is quickly closed. This occurs in the following manner:

As the disk 5| begins to rise with respect to the tapered surrounding walls 43 to a position, for example, shown in dotted lines at A (Figa) the passage for fluid around its edges is reduced in cross section and this immediately results in further and accelerated movement of the disk upwardly. As the disk reaches the position indicated at B, Fig. 2, its edges are almost, though not quite in contact with the interior cylindrical surface of the wall portion 9|, and pressure builds up very rapidly Within the pressure chamber. At this point the washer 50 on the valve stem contacts the washer 83 which is held down by the strong spring 8| mentioned above. Nevertheless, the pressure on the disk 5| is sufficient now to overcome the force ofthe strong spring 8| and thereupon the washer 83 is moved upwardly and the valve disk 5| quickly and firmly seats against the seat member 93, completely stopping further ow of fluid through the unloader. This operation may occur within a singlecycle of the compressor. hence the opening and closing of. theunloader is very Arapid and `in fac-t, almost instantaneous; lBut itkdoes not occur.; until* abminimum predetermined operating speed has been "attained such ,that the regular operatngjwindi'ngsof' the, 'driving motor may carry theload, permitting the ,starting windings to be thrown out of operation.l`

i During regular operation of vthe compressor, the 4unl'iader remainsclosed Tand nofluid escapes through the-unloader. I'Ihevalve yseat 93 is replaceable if wearshould occur permitting leakage through the 'ports94 and IB.. When the compresser lis being shut down.' an operation somewhat the reverse .ofthe vabove occurs aswill now be described. f

As the operating speed of the compressor becomes less and less, and reaches a point where the pressure inthe kpressure chamber 32 may be materially reduced during va vsingle `cycle lby outward iiow of fluid through lthe small' port 34, a sufficient reduction in ,this pressure permits the strong spring`8| tofsnap the valve disk -5| from its .uppermost position, indicated at C, Fig. 2, tol an intermediater position as at B. At the same time, the light lspring y|58 tends to force the disk 5| back toits extreme lower position where it is shown lin full lines in Fig. 2. At the point where the flow ofiiuid is not's'uic'ient to overcome these springs the valve is quickly opened to the full position `and thereupon the unloader is thrown into fullfoperation. Hence during both starting and stopping operations the unloader operates totake an undesirable load 01T the vdrivinglmotor. The operation is very rapid in either case, 'occurring substantially during one operating cycle kof the compressor.

If the output side of the unloader described above is connected to the intake side of the same compressor stagejthe device operates on a pressure diierentialbetweenthe discharge pressure of the particular compressor Stage and the inlet pressure of the same stage or cylinder on which the unloader is placed. Hence if this device is employed at the second stage of a two stage compressor, the operating range for the unloader is between the output pressure of the first stage and the output pressure of the second stage to which the unloader is attached. Hence it will be unders-tood that the device is not necessarily limited in use to a single stage compressor and in fact, it may be placed on either or both stages.

By means of the adjustments provided, as described above. the unloader can be adjusted for use over a wide range of compressor capacities.

Their range can be further extended by the substitution of elements such as the disk 33 and the valve seat member 93 having orifices of different sizes to respond to dierent speeds of operation or to different volumes of compressed fluid delivered per unit of time. For certain purposes the adjustable features for spring tension may be eliminated thus simplifying the construction to some extent if it is found that the device will be operated. over a substantially constant range or with a particular typevof compressor unit. Thus in some cases a simple unit.

where the springs 68 and 8| abut against fixed elements rather than against adjustable sleeves such as 'H and 14, may be distinctly advan- Itageous. In other cases, it will be found desirable to retain the adjustable features since they permit use of the unloader with various compressor units and for various operating ranges in speed, volume, and pressure.

.While I havev vdescribed 'the aboveinvention in connection'withan 'aircompresson it will be understoodthat it may be used Withvarious other typesof mechanisms' wherever iluid is. being compressed ata stage ofjanA operation, and where it is desirable to relieve the: working load imposed on a driver by unloading rthe fluidcompression stage. t 'f Y YHence, while'Ihave illustrated and described the preferredembodiments ofp my invention, it is to beunderstoodthat'these are capable of variationandmodication and I therefore do not wish .to be limited to the precisevdetails set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims. Y

jlj. In anunloader of the'character described comprising a baseand body'means aiording a pressure chamber having lend walls and a side wall of generally cylindrical/form, aninlet port providedin one of the end walls and opening into thepressurejchamber, 'an outlet port in the other of 'the end walls and leading from the pressure chamber, said pressure chamber having a conical portion converging toward the outlet port, a valve member carried at one end of a valve stem that is centrally mounted in the body means for vertical shifting 'movement the valve member being positioned transverselyy in said chamber for sliding movement axially thereto and adapted to movebe'tween the ports, the valve member comprising adisc-like element adjacent its top, the disc-like Velement having a diameter slightly smaller 'than the smallestdiameter of the said conical portion, the valve stembeing of a length corresponding substantially toj that of the body means and extending through the outlet port, a washer slidable in the body means and restable on an abutment afforded internally of the body means above the outlet port, a first elongated sleeve adjustably mounted in the body means concentric to' the valve stem and compressing a rst spring against the washer, the saidl rst spring being concentric tothe valve stem, abutment means carried by the valve stem above the outlet port and below Vthe washer and adapted to move with the'valve stem into engagement with the washerl whereby the valve stem is moveable against the action of the said first spring, a second elongated sleeve adjustably mounted in the rst sleeve and being concentricA to the valve stem, a third elongated sleeve slidably mounted in the second sleeve and being in concentric free engagement with the upper extension of the valve stem, the lower'end of the third sleeve being freely engageable with the top surface of the washer, a second spring concentric to the upper extension of the valve stem and urging the lower end of the third sleeve into engagement with the top surface o f the washer, the rst spring being concentric to the' second spring, the second spring being held compressed by the lower end of the second sleeve, the upper end of the valve stem being threaded to the upper end of the third sleeve vwhereby the valve stern is adjustable in the third sleeve, the distance between the said abutment means and the said washer being less than the distance between the said disc-like element and the outlet port, the second spring being more readily compressible than the rst spring.

2. In the unloader according to claim l, a check valve in the pressure chamber overlying the inlet port and being in alignment with the bottom of the valve member.

BURR W. MANTLE.

REFERENCES CITED The following references are of record inthe file` of this patent:

UNITED STATES PATENTS 2,404,924 Sacchini July 30,11946 

